4 A FIRST CHAPTER 
in time. For the reason that the simpler forms of life appeared first, it 
is thought that plants preceded animals, and as the lowest forms of each 
are almost indistinguishable from one another, both may have been 
derived from the same simple organism. While this belief is entirely 
probable, it may never be actually proved: because the small, soft, 
simple animals and plants could leave no trace of their former presence 
in the shape of fossils; and the only animals found are those high 
enough in the scale of life to possess hard parts that could be preserved 
as fossils. 
As living things increased in the world, they were influenced by 
their surroundings, and affected by the amount of light and heat, of 
rest or movement, to which they were subjected. . In places favorable 
to their growth and increase, they multiplied to such an extent that they 
began to crowd one another, and localities suitable for the support of a 
limited number were even overpopulated, and it became a question 
as to which should survive. Thus, almost at the outset arose the . 
Struggle for Existence, but it must be borne in mind that this was 
not an active struggle, but usually a mere passive effort to endure— 
such animals as by their strength, powers of endurance, and ability to 
withstand changes of climate and to resist heat or cold, being those that 
survived, while the weaker or less fit were swept out of existence. This 
is the very simplest form of the Survival of the Fittest; among 
higher animals the process is vastly more complicated, and the means by 
which it is accomplished so varied as to be almost infinite. It is neverthe- 
less purely passive on the part of the animals, not being brought about 
by any thought or conscious effort on their part. Animals think to a 
certain extent, but the reader is cautioned to beware of ascribing to 
other animals the thoughts and feelings of man; this is the more 
important, as so many books have been written in which animals are 
made to feel, and think, and act like human beings, the height of absurdity 
being reached when these thoughts and feelings are ascribed to plants. 
The care of birds for their young is often cited as a beautiful example of 
parental tenderness; but while birds, it is true, care a great deal for their 
young, it is not much in the manner in which human parents care for 
their children. The bird that will do all in her power one season to pre- 
serve her offspring, will transfer her affections the very next year to a 
new brood, and treat last year’s family as strangers, or even enemies. 
Bats furnish a good example of what may be called passive resist- 
ance. These active little animals are for the most part insectivorous— 
insect eaters, and dependent entirely on the presence of insects for their 

